The present invention relates to a multiple stage reactor system which is particularly useful in the vapor phase conversion of various hydrocarbon feedstocks. The reactor system provides for the processing of a reactant stream through two or more vertically spaced reaction chambers, said reactant stream being processed in radial flow contact with catalyst particles that are movable through said reaction chambers as a plurality of annular-form beds via gravity flow.
Various vapor phase conversion processes have heretofore been effected utilizing a reactor system wherein a reactant stream is processed in radial flow through a vertically positioned annular-form catalyst bed--an arrangement that offers many design and operating advantages, particularly with respect to those vapor phase processes for the conversion of hydrocarbons. Illustrative of a reactor system wherein a reactant stream is caused to flow laterally and radially through an annular-form catalyst bed is that described in U.S. Pat. No. 2,683,654. The reactor system illustrated is intended for a fixed bed operation. A reactant stream charged to a reaction chamber flows from an outer annular-form space created between the chamber walls and the annular-form catalyst bed, said stream flowing laterally and radially through said catalyst bed and into a perforated centerpipe to be discharged from the reaction chamber. U.S. Pat. No. 3,692,496 describes a somewhat related reactor system in that a reactant stream charged to a reaction chamber is caused to flow laterally and radially from an outer annular-form space through an annular-form catalyst section and into an inner or center manifold to be discharged from said chamber. In the latter case, the reactor system comprises stacked reaction chambers (and consequently stacked annular-form catalyst sections) designed to process catalyst particles downwardly via gravity flow from one annular-form catalyst section to the next lower annular-form catalyst section, the catalyst particles being recovered from the lowermost reaction chamber for regeneration. A variation of the last-described reactor system appears in U.S. Pat. No. 3,725,248 wherein the annular-form catalyst sections are individually contained in side-by-side reaction chambers and in U.S. Pat. No. 3,882,015 wherein the reactant stream is reversed to flow laterally and radially from a center reactant conduit through an annular-form catalyst section and into an outer annular-form space formed by the annular-form catalyst section and the reaction chamber walls.
In addition to the foregoing reactor systems in which the reactant stream is processed laterally and radially across an annular-form catalyst bed, reactor systems comprising multiple catalyst beds in a single reactor vessel have been utilized. For example, U.S. Pat. No. 4,040,794 discloses a reactor wherein the reactants flow laterally and radially across an annular-form moving catalyst bed. However, this reactor system also employs baffles attached along the sides of the annular-form catalyst bed to channel reactant flow in such a manner as to create several distinct serially connected catalyst beds from a single bed of catalyst within one reactor vessel. U.S. Pat. No. 2,617,718 discloses a further reactor system of the stationary type comprising a reactor housing with a plurality of catalyst containers located therein. The catalyst containers are depicted an annular-form catalyst beds emplaced within foraminous containers. The inlet and outlet baffles as well as the emplacement of the catalyst containers act to channel reactant flow in such a manner as to create a plurality of catalyst beds in parallel arrangement. In addition, there are baffles situated around and within each catalyst container to promote uniform flow of reactants across the annular-form catalyst beds.
The foregoing reactor systems have heretofore been described with respect to vapor phase conversion processes wherein they are employed to effect a number of catalyst-promoted conversions. Prominent among such conversion processes are the hydrocarbon conversion processes and include catalytic reforming, hydrogenation, hydrocracking, hydrorefining, isomerization and dehydrogenation, as well as alkylation, transalkylation, steam reforming and the like. The reactor system of the present invention can be similarly employed, but is of particular advantage with respect to a relatively low pressure operation, such as propane and/or butane dehydrogenation at near atmospheric pressures.